These studies are directed towards the elucidation of the function of low molecular weight methylated RNA. These are a ubiquitous class of RNA of 4-7S found in various parts of the cell: microsomal membranes, nucleolus, nuclei, and ribonucleoprotein particles of cytoplasmic and nuclear origin. These ribonucleoprotein particles are about 20S in size. We have found a large amount of the cells aminoacyl-tRNA synthetase complement to be associated with particles of this size. An analysis of the complete distribution of these synthetases shows them to be distributed differentially throughout many cell fractions.